1. Field of the Invention
Methods and apparatuses consistent with the present invention relate to a multi-band orthogonal frequency division multiplexing (OFDM). More particularly, the present invention relates to a method of implementing a clear channel assessment (CCA) function in a multi-band OFDM system of providing a relatively accurate CCA performance, and an apparatus for performing the method.
2. Description of Related Art
A multi-band orthogonal frequency division multiplexing (OFDM) generally relates to a method of an OFDM symbol hopping between frequencies among a plurality of frequency bands every predetermined symbol unit and transmitting a signal, and more particularly, to a modulation technology used for a particular wireless communication system such as an ultra wideband (UWB) system. The multi-band OFDM system may transmit and receive a large amount of data every unit hour by transmitting data using the plurality of frequency bands having a regular frequency band.
The multi-band OFDM system provides a clear channel assessment (CCA) function of detecting whether a frequency band intended to be used is currently used by another device, and may be mainly divided into a cross correlation method or an energy detection method. Since the cross correlation method is excellent in a performance aspect regardless of channel, and may be simply applied to a preamble, it is difficult to detect a signal for a period of time of 4.6875 μs corresponding to a predetermined interval of 15 OFDM symbols when considering a random point in time of detecting the CCA.
However, since the energy detection method corresponds to a method of estimating an energy of a received signal, and comparing an amount of the energy of the received signal with a specific critical value, there is an advantage that the method may be simply applied regardless of whether the received signal corresponds to a preamble or a payload. Efforts for correctly determining a channel status by using the energy detection method having the advantage are currently underway.
Therefore, a method of implementing a clear channel assessment (CCA) function in a multi-band OFDM system of providing a relatively accurate CCA performance, and an apparatus for performing the method is needed.